Glyphosate (N-(phosphonomethyl) glycine) is abroad-spectrum systemicherbicide usedto kill weeds, especially annualbroadleaf weeds and grasses known to compete with crops grownwidely across the Midwest. Initially patented and sold by MonsantoCompany in the 1970s under the tradename Roundup,its U.S. patentexpired in 2000. Glyphosate is the most used herbicide in theUSA,^{[3]where every year, 5–8 million pounds (2,300–3,600 tonnes) are usedon lawns and yards and another 85–90 million pounds(39,000–41,000 t) are used in agriculture.[3]}

Glyphosate''s mode of action is to inhibit an enzyme involved in thesynthesis of the aromatic aminoacids: tyrosine, tryptophan andphenylalanine. Itis absorbed through foliage and translocated to growing points.Because of this mode of action, it is only effective on activelygrowing plants; it is not effective as a pre-emergenceherbicide.

Some crops have been geneticallyengineered to be resistant to it (i.e. Roundup Ready). Suchcrops allow farmers to use glyphosate as a post-emergence herbicideagainst both broadleaf and cereal weeds, but the development ofsimilar resistance in some weed species is emerging as a costlyproblem. Soy was the first Roundup Ready crop.